Contents
CMake provides a file-based API that clients may use to get semantic information about the buildsystems CMake generates. Clients may use the API by writing query files to a specific location in a build tree to request zero or more Object Kinds. When CMake generates the buildsystem in that build tree it will read the query files and write reply files for the client to read.
The file-based API uses a <build>/.cmake/api/ directory at the top of a build tree. The API is versioned to support changes to the layout of files within the API directory. API file layout versioning is orthogonal to the versioning of Object Kinds used in replies. This version of CMake supports only one API version, API v1.
API v1 is housed in the <build>/.cmake/api/v1/ directory. It has the following subdirectories:
Holds reply files written by CMake whenever it runs to generate a build system. These are indexed by a v1 Reply Index File file that may reference additional v1 Reply Files. CMake owns all reply files. Clients must never remove them.
Clients may look for and read a reply index file at any time. Clients may optionally create the reply/ directory at any time and monitor it for the appearance of a new reply index file.
Client stateless query files allow clients to create owned requests for major versions of the Object Kinds and get all requested versions recognized by the CMake that runs.
Clients may create owned requests by creating empty files in client-specific query subdirectories. The form is:
<build>/.cmake/api/v1/query/client-<client>/<kind>-v<major>
where client- is literal, <client> is a string uniquely identifying the client, <kind> is one of the Object Kinds, -v is literal, and <major> is the major version number. Each client must choose a unique <client> identifier via its own means.
Files of this form are stateless queries owned by the client <client>. The owning client may remove them at any time.
Stateful query files allow clients to request a list of versions of each of the Object Kinds and get only the most recent version recognized by the CMake that runs.
Clients may create owned stateful queries by creating query.json files in client-specific query subdirectories. The form is:
<build>/.cmake/api/v1/query/client-<client>/query.json
where client- is literal, <client> is a string uniquely identifying the client, and query.json is literal. Each client must choose a unique <client> identifier via its own means.
query.json files are stateful queries owned by the client <client>. The owning client may update or remove them at any time. When a given client installation is updated it may then update the stateful query it writes to build trees to request newer object versions. This can be used to avoid asking CMake to generate multiple object versions unnecessarily.
A query.json file must contain a JSON object:
{
"requests": [
{ "kind": "<kind>" , "version": 1 },
{ "kind": "<kind>" , "version": { "major": 1, "minor": 2 } },
{ "kind": "<kind>" , "version": [2, 1] },
{ "kind": "<kind>" , "version": [2, { "major": 1, "minor": 2 }] },
{ "kind": "<kind>" , "version": 1, "client": {} },
{ "kind": "..." }
],
"client": {}
}
The members are:
A JSON array containing zero or more requests. Each request is a JSON object with members:
Indicates the version(s) of the object kind that the client understands. Versions have major and minor components following semantic version conventions. The value must be
For each requested object kind CMake will choose the first version that it recognizes for that kind among those listed in the request. The response will use the selected major version with the highest minor version known to the running CMake for that major version. Therefore clients should list all supported major versions in preferred order along with the minimal minor version required for each major version.
Other query.json top-level members are reserved for future use. If present they are ignored for forward compatibility.
CMake writes an index-*.json file to the v1/reply/ directory whenever it runs to generate a build system. Clients must read the reply index file first and may read other v1 Reply Files only by following references. The form of the reply index file name is:
<build>/.cmake/api/v1/reply/index-<unspecified>.json
where index- is literal and <unspecified> is an unspecified name selected by CMake. Whenever a new index file is generated it is given a new name and any old one is deleted. During the short time between these steps there may be multiple index files present; the one with the largest name in lexicographic order is the current index file.
The reply index file contains a JSON object:
{
"cmake": {
"version": {
"major": 3, "minor": 14, "patch": 0, "suffix": "",
"string": "3.14.0", "isDirty": false
},
"paths": {
"cmake": "/prefix/bin/cmake",
"ctest": "/prefix/bin/ctest",
"cpack": "/prefix/bin/cpack",
"root": "/prefix/share/cmake-3.14"
},
"generator": {
"multiConfig": false,
"name": "Unix Makefiles"
}
},
"objects": [
{ "kind": "<kind>",
"version": { "major": 1, "minor": 0 },
"jsonFile": "<file>" },
{ "...": "..." }
],
"reply": {
"<kind>-v<major>": { "kind": "<kind>",
"version": { "major": 1, "minor": 0 },
"jsonFile": "<file>" },
"<unknown>": { "error": "unknown query file" },
"...": {},
"client-<client>": {
"<kind>-v<major>": { "kind": "<kind>",
"version": { "major": 1, "minor": 0 },
"jsonFile": "<file>" },
"<unknown>": { "error": "unknown query file" },
"...": {},
"query.json": {
"requests": [ {}, {}, {} ],
"responses": [
{ "kind": "<kind>",
"version": { "major": 1, "minor": 0 },
"jsonFile": "<file>" },
{ "error": "unknown query file" },
{ "...": {} }
],
"client": {}
}
}
}
}
The members are:
A JSON object containing information about the instance of CMake that generated the reply. It contains members:
A JSON object specifying the version of CMake with members:
A JSON object describing the CMake generator used for the build. It has members:
A JSON object mirroring the content of the query/ directory that CMake loaded to produce the reply. The members are of the form
A member of this form appears for each client-owned directory holding v1 Client Stateless Query Files. The value is a JSON object mirroring the content of the query/client-<client>/ directory. The members are of the form:
This member appears for clients using v1 Client Stateful Query Files. If the query.json file failed to read or parse as a JSON object, this member is a JSON object with a single error member containing a string with an error message. Otherwise, this member is a JSON object mirroring the content of the query.json file. The members are:
If the query.json file requests member is missing or invalid, this member is a JSON object with a single error member containing a string with an error message. Otherwise, this member contains a JSON array with a response for each entry of the requests array, in the same order. Each response is
After reading the reply index file, clients may read the other v1 Reply Files it references.
The reply index file represents each reference to another reply file using a JSON object with members:
Reply files containing specific Object Kinds are written by CMake. The names of these files are unspecified and must not be interpreted by clients. Clients must first read the v1 Reply Index File and and follow references to the names of the desired response objects.
Reply files (including the index file) will never be replaced by files of the same name but different content. This allows a client to read the files concurrently with a running CMake that may generate a new reply. However, after generating a new reply CMake will attempt to remove reply files from previous runs that it did not just write. If a client attempts to read a reply file referenced by the index but finds the file missing, that means a concurrent CMake has generated a new reply. The client may simply start again by reading the new reply index file.
The CMake file-based API reports semantic information about the build system using the following kinds of JSON objects. Each kind of object is versioned independently using semantic versioning with major and minor components. Every kind of object has the form:
{
"kind": "<kind>",
"version": { "major": 1, "minor": 0 },
"...": {}
}
The kind member is a string specifying the object kind name. The version member is a JSON object with major and minor members specifying integer components of the object kind’s version. Additional top-level members are specific to each object kind.
The codemodel object kind describes the build system structure as modeled by CMake.
There is only one codemodel object major version, version 2. Version 1 does not exist to avoid confusion with that from cmake-server(7) mode.
codemodel object version 2 is a JSON object:
{
"kind": "codemodel",
"version": { "major": 2, "minor": 1 },
"paths": {
"source": "/path/to/top-level-source-dir",
"build": "/path/to/top-level-build-dir"
},
"configurations": [
{
"name": "Debug",
"directories": [
{
"source": ".",
"build": ".",
"childIndexes": [ 1 ],
"projectIndex": 0,
"targetIndexes": [ 0 ],
"hasInstallRule": true,
"minimumCMakeVersion": {
"string": "3.14"
}
},
{
"source": "sub",
"build": "sub",
"parentIndex": 0,
"projectIndex": 0,
"targetIndexes": [ 1 ],
"minimumCMakeVersion": {
"string": "3.14"
}
}
],
"projects": [
{
"name": "MyProject",
"directoryIndexes": [ 0, 1 ],
"targetIndexes": [ 0, 1 ]
}
],
"targets": [
{
"name": "MyExecutable",
"directoryIndex": 0,
"projectIndex": 0,
"jsonFile": "<file>"
},
{
"name": "MyLibrary",
"directoryIndex": 1,
"projectIndex": 0,
"jsonFile": "<file>"
}
]
}
]
}
The members specific to codemodel objects are:
A JSON object containing members:
A JSON array of entries corresponding to available build configurations. On single-configuration generators there is one entry for the value of the CMAKE_BUILD_TYPE variable. For multi-configuration generators there is an entry for each configuration listed in the CMAKE_CONFIGURATION_TYPES variable. Each entry is a JSON object containing members:
A JSON array of entries each corresponding to a build system directory whose source directory contains a CMakeLists.txt file. The first entry corresponds to the top-level directory. Each entry is a JSON object containing members:
Optional member present when a minimum required version of CMake is known for the directory. This is the <min> version given to the most local call to the cmake_minimum_required(VERSION) command in the directory itself or one of its ancestors. The value is a JSON object with one member:
A string specifying the minimum required version in the format:
<major>.<minor>[.<patch>[.<tweak>]][<suffix>]
Each component is an unsigned integer and the suffix may be an arbitrary string.
A JSON array of entries corresponding to the top-level project and sub-projects defined in the build system. Each (sub-)project corresponds to a source directory whose CMakeLists.txt file calls the project() command with a project name different from its parent directory. The first entry corresponds to the top-level project.
Each entry is a JSON object containing members:
A JSON array of entries corresponding to the build system targets. Such targets are created by calls to add_executable(), add_library(), and add_custom_target(), excluding imported targets and interface libraries (which do not generate any build rules). Each entry is a JSON object containing members:
A codemodel “target” object is referenced by a “codemodel” version 2 object’s targets array. Each “target” object is a JSON object with members:
Optional member that is present when the FOLDER target property is set. The value is a JSON object with one member:
A JSON object containing members:
Optional member that is present for executable and library targets that produce artifacts on disk meant for consumption by dependents. The value is a JSON array of entries corresponding to the artifacts. Each entry is a JSON object containing one member:
Optional member that is present when the target has an install() rule. The value is a JSON object with members:
A JSON object specifying the installation prefix. It has one member:
A JSON array of entries specifying an install destination path. Each entry is a JSON object with members:
Optional member that is present for executables and shared library targets that link into a runtime binary. The value is a JSON object with members describing the link step:
Optional member that is present when fragments of the link command line invocation are available. The value is a JSON array of entries specifying ordered fragments. Each entry is a JSON object with members:
A string specifying the role of the fragment’s content:
Optional member that is present when the CMAKE_SYSROOT_LINK or CMAKE_SYSROOT variable is defined. The value is a JSON object with one member:
Optional member that is present for static library targets. The value is a JSON object with members describing the archive step:
Optional member that is present when fragments of the archiver command line invocation are available. The value is a JSON array of entries specifying the fragments. Each entry is a JSON object with members:
A string specifying the role of the fragment’s content:
Optional member that is present when the target depends on other targets. The value is a JSON array of entries corresponding to the dependencies. Each entry is a JSON object with members:
A JSON array of entries corresponding to the target’s source files. Each entry is a JSON object with members:
Optional member that is present when sources are grouped together by the source_group() command or by default. The value is a JSON array of entries corresponding to the groups. Each entry is a JSON object with members:
Optional member that is present when the target has sources that compile. The value is a JSON array of entries corresponding to groups of sources that all compile with the same settings. Each entry is a JSON object with members:
Optional member that is present when fragments of the compiler command line invocation are available. The value is a JSON array of entries specifying ordered fragments. Each entry is a JSON object with one member:
Optional member that is present when there are include directories. The value is a JSON array with an entry for each directory. Each entry is a JSON object with members:
Optional member that is present when target_precompile_headers() or other command invocations set PRECOMPILE_HEADERS on the target. The value is a JSON array with an entry for each header. Each entry is a JSON object with members:
This field was added in codemodel version 2.1.
Optional member that is present when there are preprocessor definitions. The value is a JSON array with an entry for each definition. Each entry is a JSON object with members:
Optional member that is present when the CMAKE_SYSROOT_COMPILE or CMAKE_SYSROOT variable is defined. The value is a JSON object with one member:
A JSON object describing the graph of backtraces whose nodes are referenced from backtrace members elsewhere. The members are:
A JSON array listing nodes in the backtrace graph. Each entry is a JSON object with members:
The cache object kind lists cache entries. These are the Variables stored in the persistent cache (CMakeCache.txt) for the build tree.
There is only one cache object major version, version 2. Version 1 does not exist to avoid confusion with that from cmake-server(7) mode.
cache object version 2 is a JSON object:
{
"kind": "cache",
"version": { "major": 2, "minor": 0 },
"entries": [
{
"name": "BUILD_SHARED_LIBS",
"value": "ON",
"type": "BOOL",
"properties": [
{
"name": "HELPSTRING",
"value": "Build shared libraries"
}
]
},
{
"name": "CMAKE_GENERATOR",
"value": "Unix Makefiles",
"type": "INTERNAL",
"properties": [
{
"name": "HELPSTRING",
"value": "Name of generator."
}
]
}
]
}
The members specific to cache objects are:
A JSON array whose entries are each a JSON object specifying a cache entry. The members of each entry are:
A JSON array of entries specifying associated cache entry properties. Each entry is a JSON object containing members:
The cmakeFiles object kind lists files used by CMake while configuring and generating the build system. These include the CMakeLists.txt files as well as included .cmake files.
There is only one cmakeFiles object major version, version 1.
cmakeFiles object version 1 is a JSON object:
{
"kind": "cmakeFiles",
"version": { "major": 1, "minor": 0 },
"paths": {
"build": "/path/to/top-level-build-dir",
"source": "/path/to/top-level-source-dir"
},
"inputs": [
{
"path": "CMakeLists.txt"
},
{
"isGenerated": true,
"path": "/path/to/top-level-build-dir/.../CMakeSystem.cmake"
},
{
"isExternal": true,
"path": "/path/to/external/third-party/module.cmake"
},
{
"isCMake": true,
"isExternal": true,
"path": "/path/to/cmake/Modules/CMakeGenericSystem.cmake"
}
]
}
The members specific to cmakeFiles objects are:
A JSON object containing members:
A JSON array whose entries are each a JSON object specifying an input file used by CMake when configuring and generating the build system. The members of each entry are: